How the moon got its sunburn

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Research using data from NASA’s ARTEMIS mission suggests that some of the coloration we see on the moon could be a form of sunburn.

Here on Earth, we’re largely protected from the damaging effects of the solar wind – the stream of charged particles released from the sun’s upper atmosphere. That’s because the solar wind is magnetized, and Earth’s natural magnetic field deflects the solar wind particles around our planet so that only a small fraction of them reach our planet’s atmosphere.

But the moon has no global magnetic field. Magnetized rocks near the lunar surface, however, do create small, localized spots of magnetic field – small bubbles of magnetic “sunscreen” – that extend anywhere from hundreds of yards to hundreds of miles.

Under these miniature magnetic umbrellas, the material that makes up the moon’s surface, called regolith, is shielded from the sun’s particles. As those particles flow toward the moon, they are deflected to the areas just around the magnetic bubbles, where chemical reactions with the regolith darken the surface. This creates the distinctive patterns of darker and lighter swirls that are so prominent they can be seen from Earth.

Light colored oval and wiggly lines on darker gray lunar surface.
Research suggests that lunar swirls, like the Reiner Gamma lunar swirl imaged here by NASA’s Lunar Reconnaissance Orbiter, could be the result of solar wind interactions with the moon’s isolated pockets of magnetic fields. More about this image. Image via NASA LRO WAC science team.

Bottom line: Video on how the moon got its distinctive pattern of lighter and darker swirls.


March 7, 2019

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